agnosticbin: get a reference of the event
agnosticbin: get a reference of the event

Event reference is lost calling to gst_pad_event_default.

Change-Id: I1d809df0fc90769dc09d5601c95f7c390809f315

Kurento/kms-elements,Kurento/kms-elements,Kurento/kms-elements,TribeMedia/kms-elements,TribeMedia/kms-elements,shelsonjava/kms-elements,shelsonjava/kms-elements,shelsonjava/kms-elements,TribeMedia/kms-elements